1. Field of the Invention
The present invention relates to an apparatus for the preparing of coffee for an application in an automatic coffee-percolator, including a scalding cylinder intended for receipt of ground coffee, opposite pistons for the compressing of the ground coffee and means for feeding water or steam and for discharging the prepared coffee.
2. Description of the Prior Art
Such an apparatus, also termed extraction apparatus and including aforementioned devices is disclosed e.g. in the European Specification No. EP 0 202 517.
Accordingly, ground coffee is for instance fed in through a lateral opening in a scalding cylinder which is open at both ends of which one opening is closed off by the surface of one of the pistons and the other opening still remains open. During a further step the first piston moves now into the stationary scalding cylinder and towards the opening which now has been closed off by the second piston by a movement in the opposite direction. This causes the ground coffee to be moved away from the lateral infeed opening towards one of the ends of the scalding cylinder and be compressed as far as the first piston is moved with the aid of a contacting device which stops the movement of the piston as soon as the piston which is freely axially movable against the action of a spring has run through a predetermined spring travel stroke.
Through the ground coffee which accordingly has been thus compressed in a controlled manner water or steam supplied for instance through an axial bore in one of the piston rods is led through the scalding chamber filled with the ground coffee and the coffee thus made is led off through e.g. a similar bore in the other piston rod. The second piston is thereafter again moved into its initial position and the portion of coffee grinds pushed out by a further movement of the first piston in its initial direction of movement. Finally, the first piston moves also in the scalding cylinder into its starting position.